(Classroom notes distributed 8/30/2002)

Types of Operation:

1. Batch Operation:

1. Feed is charged into vessel
2. Process is started
3. No mass is added or removed from vessel ( temperature and pressure are usually monitored and controlled )
4. At some conditions or fixed time, products are removed

0. Continuous Operation: input and output flow continuously
1. Semi-batch Operation: neither batch nor continuous

General Balance Equation

Main Principle: mass is always conserved, i.e. mass can not be created nor destroyed

Types of Process Condition:

1. Transient : values are changing with time
2. Steady State: values are not changing with time ( rate of accumulation = 0 )

COMPONENT MASS BALANCE:

INTEGRAL BALANCES:

• balance describing changes between two instants of time
• instead of rates, the balance describes what happens to amounts of balance quantities.

COMPONENT MASS INTEGRAL BALANCE:

NOTE: For a batch process, if we let t₁ be the time prior to charging the feed and let t₂ be the time after all the products are removed, then the amount accumulated is still 0. Thus in this special case,
 
 

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Flowcharts

Guidelines:

1. Understand the process
2. Be careful of the arrows
3. Take gravity into consideration

• use x for mole or mass fraction of heavier components
• use y for mole or mass fraction of lighter components
• use z for mole or mass fraction of feed

1. Note that some streams do not necessarily mix (ex. heat exchangers)

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